Method of and apparatus for continuous flow densifiers



Oct. 9, 1951 M|TTEN 2,570,367

METHOD OF AND APPARATUS FOR CONTINUQUS FLOW DENSIFIERS Filed March 25, 1948 FIE! Q i i Q S a'? 27 INVENTDR R. E M/TTEN Patented Oct. 9, 1951 UNITED STAT-ES P TENT OFFICE METHOD DEAND APPABATUS FOR CON-'- IIINUOUS :FLoW DENSIFIERS Raymond F. Mitten, Cleveland, Ohio, .assignor to "The Yo'derfCoinpaiiy, Cleveland, Ohio, a'corpo- This invention relates to a continuous flow densifying method and apparatus, especially "to an apparatus and method for use in feeding aggregates to continuous'concrete mixers wherein.such aggregates are fed at a constant rate dependent upon the dry weight of such aggregates, although the present invention is also applicable to other fields, such as control of the mixture of foundry sandrand binders.

In previous manufacturing of concrete by batch processes, it is common practice to proportion cement and aggregates by weight, or by volume in the manufacture of concrete and concrete products. Proportioning by weight-involves the use of complicated and costly batch weighing equipment that requires considerable manepower for its operation. Recently the concrete industry has been changing over to continuous type of concrete mixers wherein the ingredients are continuously fed into the mixer at one portion thereof and continuously discharged from another portion of the mixer. When using continuous mixers for concrete, :it is possible to-feed the mixers by weight proportioning only through the use of costly, bulky, complicated constant weight feeding devices. Then too, some continuous mixers are fed by volume of aggregates'but as thevolume of .=various aggregates change due to moisture content, therelation between the aggregate.an'dP-ortland cement varies greatly and consequently undesirably alters the properties of the concrete produced. These devices haveop erated'updnvarious principles, but have in all instances, been complex mechanisms that are objectionable, both because of their "original -cost and because of their maintenancerequire'd on "suchdevices tokeep them operating satisfactorily. 'Of course, *withexpansion of the concrete industry and'with the use of new types of aggregates, larger continuous mixers are being used today and these mixers, and any constant Weight feeders provided therefor. have had "proportioned increases in maintenance and power costs.

The continuous type-ofconcrete mixer has established itself as a very satisfactory piece of apparatus that produces a desired-quality ofzmix with low power and maintenance cost per cubic yard of material produced. :AlsothaiiiitialcoSt 'has not been excessive'withthe exceptionof the relatively complex, sensitive constant weight feeder'device'used. I

'As indicated hereinbefore, it has been known that the various aggregates *used .-in concrete manufactu'regsuch as sand, gravel -slag, cinders,

haydite, or other fine or loose'material'vari'es'in .volume with the amount of water present in the aggregate. Thus the use of any constant volume type of feeder for a continuous .mixer is not accurate'since varying amounts of the aggregate wouldbe delivered dependent upon the moisture content of same.

It has been satisfactory to use constant weight feeder devices .because the weight of the water present in the aggregate has not upset the desired ratios, or proportions of the aggregates to the other components of the concrete being produced. The moisture content of an aggregate may vary from approximately 0% moisture up to as high as about 20% mois- ,-ture content, since higher moisture. contents usuallyrender the aggregate undesirable for use until it has been reduced to a'lower moisture content.

.The general object of thepresentinvention is tolprovide an apparatus and method for use in continuously supplying constant weight quantities of aggregate, based on the dry aggregate present, regardless of the moisture content and original volume ofsuch aggregate.

Another object of the invention isto reduce any aggregate to a standard volume regardless of the moisture content of same.

Another object of the invention is to rovide inexpensive, sturdy apparatus for continuously withdrawing a constant volume of aggregate from a-storage hopper.

A'furth r object of the invention is to densify material in \a storage hopper so asto permit uniform discharge of effective dry weights of .suchmaterial.

r Attention is directed to the accompanying drawings, wherein:

Fig. 1 is a side elevation,partiallyain section,

of apparatus of the invention; and

Fig. "2 is a fragmental vertical section taken on line 22 of Figjl.

Throughout the specification and drawings, similar-reference characters will beuse'd'to refer to the sameparts for ease of identification of same.

The presentinvention, broadly-speakingin the method -disclosed herein, resides in the fact that I have discovered. that aggregate materials of varying moisture contents can be reduced to uni- The apparatus of the inventionbroadand at; least. partiallysupporting the contents #of the hopper, and a vibratory plate member associated with the belt and adapted to transmit vibrations through the belt to material in the hopper.

Reference is now made to the accompanying drawings, wherein Fig. 1 indicates a continuous flow densifier it. which includes a conventional hopper ii that has an open lower end or discharge section provided therefor. An aggregate material if is contained in the hopper and is fed thereto in any desired manner, either continuously or intermittently as required. The hopper H is supported by braces l3. The aggregate l2 contained in the hopper H is adapted to be at least partiall supported by means of an endless belt id, as one feature of the invention. This endless belt Hi is formed from any desired material, such as a rubber-fabric composition, and

the belt M is positioned by means of two drums l5 and it which are in spaced relation with the belt i l being substantially horizontally positioned thereby for movement immediately below the discharge portion of the hopper ii. Any conventional means, not shown, may be provided for drivin one of the drums E5 or ii; so that the belt can be rotated at a convenient speed. The hopper H has a vertically adjustable discharge gate l'l slidably positioned on one side thereof and the belt i is placed with relation to the hopper it so that the belt moves outwardly of the hopper in passing gate i? so that aggregate i2 can be carried from the hopper on the belt, as indicated.

In order to vibrate the aggregate l2 while it is in or passing through the hopper H, a plate i8 is positioned immediately under the top stretch or section of the belt Hi. This plate 18 may be formed from any desired material, usually metal, that it is of substantiall the same size as the lower portion of the hopper H. The plate l8 carries a downwardly extending bracket l9 formed to receive a transversely directed shaft 2|. The shaft 2% is smaller in diameter than the holes 22 provided in the bracket IQ for receiving the shaft 2 l. Thus an eccentric sleeve 23 can be secured to the shaft M by a key 24 whereby the eccentric sleeve 23 will rotate integrally with the shaft 2i and occasion vibratory vertical movement of the plate is as the shaft 2! is rotated. Any conventional means may drive the shaft 2| and an electric motor 25. is provided for this purpose. It will be realized that the desired vibration of the plate 2! may be effected in any desired manner and the vibration may have transverse as well as vertical components, or it may even comprise oscillations in a substantially horizontal plane.

The bracket 19 is loosely confined b means of box-like structure 26 that is supported on a frame 27 by means of brackets 28 so that movement of the plate is and associated means are limited and a safety device is provided, should the driving support means for the plate i8 fail.

The construction and arrangement of the plate i8 is such that vibration thereof is transmitted through the belt l t to the contents of the hopper H. The size of the hopper ii and the amount of aggregate material therein is so regulated that the aggregate material is subjected to a sufficient length of vibration as to reduce its volume to a constant figure which will not change with extended vibration thereof whereby removal of a constant volume of aggregate from the hopper will withdraw, in dry weight, a constant weight of the aggregate. This constant weight of aggregate withdrawn, is, it will be seen, free from and not dependent upon the amount of moisture content of such aggregate. As previously indicated, the amount of moisture in the aggregate does not interfere materially in the proportioning of a concrete mix, but it is important that constant dry weights of material be supplied.

In tests conducted upon a slag blend aggregate which was composed of expanded blast fur-- nace slag combined with fine hard slag, it was determined that a test sample contain 12 /2% moisture when a sample of such material was thoroughly dried. By measuring the volume of the sample before and after drying, it was established that the sample had a shrinkage in volume of 27.2%. Vibration of the dry sample effected a relatively rapid further shrinkage of 2.8% so that the wet sample when dried and vibrated had shrunk a total of 30%. A second sample of the same material, when treated in its original, wet condition, by vibrating same in a suitable container, had its volume reduced 30% so that the vibrated, wet sample had identical volume with the corresponding amount of the original sample that had been dried and then vibrated. Addition of 12 /2% moisture to the dried sample of aggregate resulted in a bulking or increase in volume of over of the dry volume of such material so that the bulked, dried sample returned to its original volume.

In another test upon the slag blend aggregate referred to hereinbefore, the aggregate was thoroughly dried and moisture additions of 4%, 8%, 12%, and 16% were added to test quantities.

' Bulking, or volumetric increase occurred in the samples in proportional amount to the percentage of water added thereto. However, when the moistened test aggregates were vibrated they rapidly assumed uniform volumes regardless of the moisture content of same or their previous volumes when wet and unvibrated.

In another instance tests were conducted upon fine sand which had a smaller content of fine gravel. The tested specimen was dried and then ti /2% of Water was added to the sample and thoroughly mixed therewith, which water caused the sample to become slightly gummy. A portion of the aggregate was vibrated and there was a 34% loss in volume. A second portion of the wet aggregate material was dried and the dried aggregate vibrated for a short time with the total final loss in volume of the second aggregate specimen being 34%.

In another test made upon cinders, it was determined that the cinders being tested contained 10% moisture. Corresponding samples of the cinders showed a loss of 34 in volume, both by a vibrating action and by a combined drying and vibrating action.

In view of the foregoing and other test results, it has been established that a constant volume feeder method can be used for feeding constant weights of aggregate material where one is considering the dry weights of such aggregate material and the variable water content of same is ignored. Hence the total weight of aggregate feed will vary dependent upon the moisture content of the material but predetermined amounts of aggregates, based on the dry weight of same, can be continuously and accurately mixed by the method of the invention. Thus improved mixing is effected by the invention since it overcomes the disadvantages of both'the previous constant weight and constant volume feeder devices.

It will -be -r ealized thatin some instances it may be desirable to use otlieftypes of vibratin V {a d-discharge-platethait woiil t fwould'bea t, "prefe ated. the hopper "so d'risifying action would be "completed prior to Any passage of the material from the hopper. desired siding devices may be used with or be placed on the belt M to aid in holding material thereon.

While a complete embodiment of the invention has been illustrated and described in detail herein, it will be realized that the invention is not limited to the specific example set forth since modification may be resorted to within the scope of the appended claims.

Having thus described my invention, what I claim is:

1. That method of making the volume of an aggregate, that expands as its moisture content increases, uniform regardless of the moisture content of same comprising the steps of vibrating a mass of the aggregate to condense same to a uniform volume regardless of the moisture content of same, and continuously withdrawing a constant volume of aggregate.

2. A method of continuously discharging a uniform quantity of an aggregate regardless of the moisture content of same comprising the steps of vibrating a quantity of the material to render the volume thereof uniform regardless of the moisture content of same, and feeding a constant dry weight of the material continuously from the original quantity of same by volumetrically controlling the amount of material discharged.

3. A continuous dispenser device for granular aggregate material comprising a hopper for storing the material, said hopper having an open lower end, an endless belt, a pair of spaced drum means journalling said belt with the top portion thereof being substantially horizontal and immediately below the lower end of said hopper, said belt being adapted to support the contents of said hopper, means for rotating at least one of said drum means for rotating said belt, said hopper having an adjustable discharge gate on one side of the lower portion thereof, a support plate positioned immediately below the top portion of said belt and in contact with the lower surface of same, said plate being positioned directly below the lower end of said hopper, and means for vibrating said plate associated therewith whereby material in said hopper and supported on said belt will be agitated and can be continuously discharged from said hopper by movement of said belt.

4. A continuous dispenser device for granular material comprising a hopper for storing a quantity of the material, said hopper having an open lower end, an endless belt, means journalling said belt with the top portion thereof being immediately below the lower end of said hopper to support the contents of said hopper, means for rotating said belt, said hopper having a discharge gate on one side of the lowerportion thereof, a support ,plate positioned immediately below the top portion of said belt, said plate being positioned directly below the lower end of said hopper, and means for vibrating said plate associated therewith, said plate being adapted to transmit vibrations to the material stored in said hopper.

5. A continuous dispenser device for granular tsetse having; lower end, an endless belt, means journalfing' said belt with the topportion thereof being imme diatelybelow butspabea from the lower end of said hopper to support the contents of said hopper, means for rotatingsaid 'belt, a support plate positionedimmediately below the top portion of said belt directly below the lower end of said hopper, and means for vibrating said plate, said plate being adapted to transmit vibrations through the said belt to the material stored in said hopper.

6. A continuous dispenser device for granular material comprising a hopper for storing a quantity of the material, said hopper having an open lower end, a belt, means positioning said belt with a top portion thereof below the lower end of said hopper to receive and at least partially support the contents of said hopper, a support member positioned immediately below said belt directly below the lower end of said hopper, and means for vibrating said support member whereby vibrations are transmitted to the material stored in said hopper.

'7. That method of feeding aggregates the volume of which differs with the moisture content of the aggregates comprising the steps of collecting a quantity of an aggregate, vibrating the entire quantity of such aggregate while maintained in a mass to densify same and render the volume thereof uniform regardless of the moisture content of same, retaining the aggregate in the vibrated mass until a constant volume of aggregate is obtained, and volumetrically discharging the constant volume aggregate at a uniform dry weight rate due to the uniform volume thereof.

8. That method of feeding an aggregate the volume of which differs with the moisture content of same, comprising the steps of collecting a quantity of an aggregate, vibrating the entire quantity of such aggregate while maintained in a mass to densify same and render the volume thereof uniform regardless of the moisture content of same, retaining the aggregate in the vibrated mass until a constant volume of aggregate is obtained, and continuously discharging the constant volume aggregate by a controlled volume discharge thereof.

9. A method of concentrating a material such as sand, cinders, or blast furnace slag comprising the steps of continuously feeding the material to a storage area, vibrating the material in the storage area primarily in a vertical direction, and continuously withdrawing a portion of the material from the storage area from the lowest portion thereof, which withdrawal is volumetrically controlled and with the material being retained in the storage area for suflicient time to be reduced to minimum volume prior to discharge from such area.

10. A method of concentrating and feeding a material primarily comprising sand, cinders, or blast furnace slag'the volume of which differs with the moisture content of same comprising the steps of feeding the material to a storage area to maintain a volume of material therein, vibrating the material in the storage area in substantially only a vertical direction until the material in at least the lower portion thereof is of uniform volume regardless of the moisture content of same, and controlling the volume of a discharge opening for the storage area in the lowest portion thereof to discharge desired charged.

- weights of material by control of the volumes dis- RAYMOND F. MITTEN.

REFERENCES CITED record in the Number UNITED-STATES PATENTS Name Date Chu 'ch et a1. July 3, 1923 Baker Jan. 19, 1932 7 Lowell Aug. 22, 1933 Little Dec. 7, 1937 French Oct. 25, 1938 Schweitzer Oct. 10, 1944 

